1. Field of the Invention
The present invention relates generally to a distribution cable for a fiber optic communications network, and more specifically, to a fiber optic distribution cable having one or more articulated optical connection nodes positioned along the length of the cable for providing access to at least one preterminated optical fiber.
2. Description of the Related Art
Optical fiber is increasingly being used for a variety of broadband communications including voice, video and data transmissions. As a result of the increasing demand for broadband communications, fiber optic networks typically include a large number of mid-span access locations at which one or more optical fibers are terminated from a distribution cable. These mid-span access locations provide a branch point from the distribution cable leading to another distribution point, or a drop point from the distribution cable leading to an end user, commonly referred to as a subscriber, thereby extending an “all optical” communications network closer to the subscriber. In this regard, fiber optic networks are being developed that deliver “fiber-to-the-curb” (FTTC), “fiber-to-the-business” (FTTB), “fiber-to-the-home” (FTTH), or “fiber-to-the-premises” (FTTP), referred to generically as “FTTx.” Based on the large number of mid-span access locations and the unique demands of optical fibers and optical connections, a distribution cable is needed for routing and protecting optical fibers, and for providing access to terminated optical fibers at numerous mid-span access locations in an FTTx network. A distribution cable is also needed for permitting optical fibers that are accessed and terminated from the distribution cable at mid-span access locations along the length of the distribution cable to be optically connected with optical fibers of one or more fiber optic branch cables or fiber optic drop cables.
In one example of a fiber optic communications network, one or more drop cables are interconnected with a distribution cable at a mid-span access location. Substantial expertise and experience are required to configure the optical connections in the field. In particular, it is often difficult to identify a particular optical fiber of the distribution cable to be optically connected with an optical fiber of a drop cable. Once identified, the optical fiber of the distribution cable is typically joined directly to the optical fiber of the drop cable at the mid-span access location using conventional splicing techniques, such as fusion splicing. In other instances, the optical fiber of the distribution cable and the optical fiber of the drop cable are first spliced to a short length of optical fiber having an optical connector mounted on the other end, which is generally referred to in the art as a “pigtail.” The pigtails are then routed to opposite sides of a connector adapter sleeve to interconnect the drop cable with the distribution cable. In either case, the process of configuring the mid-span access location is not only time consuming, but frequently must be accomplished by a highly skilled field technician at significant cost and under field working conditions that are less than ideal. In situations in which a mid-span access location is enclosed within a conventional splice closure, reconfiguring optical connections within the splice closure is especially difficult, based in part on the relatively inaccessible location of the closure, the limited workspace available within the closure, and the inability to readily remove the closure from the distribution cable. Further, once the spliced optical connections are made, it is labor intensive, and therefore relatively costly, to reconfigure the optical connections or to add additional spliced optical connections.
In order to reduce installation costs by permitting less experienced and less skilled technicians to make optical connections and to reconfigure optical connections at mid-span access locations in the field, communications service providers are increasingly pre-engineering new fiber optic networks and demanding factory-prepared interconnection solutions, commonly referred to as “plug-and-play” type systems. Among the currently developed plug-and-play systems, most rely on a single, rigid enclosure to house multiple optical connectors, and most require extensive field labor to configure the optical connections within the enclosure during deployment of the distribution cable or during installation of fiber optic branch cables or fiber optic drop cables. Specifically, the existing plug-and-play type systems often require that a larger diameter enclosure be added to the distribution cable after the cable is deployed through a conduit having a relatively small inner diameter. In some cases, preterminated optical fibers branched from the distribution cable are routed to respective optical connectors located within an exterior wall of a factory-prepared enclosure provided on the distribution cable. However, distribution cables provided with factory-prepared enclosures tend to be large in size and not flexible enough for common deployment methods, such as being deployed through a conduit having a relatively small inner diameter or significant bends, or being deployed using conventional aerial lashing equipment, such as sheaves and rollers. In addition, current solutions are restricted in connection node count due to the same diameter constraints, thereby making such solutions incapable of accommodating larger numbers of preterminated optical fibers (e.g., 8, 10, 12) without customization or without extensive reconstruction following deployment.
In addition, in order to terminate one or more optical fibers at a mid-span access location, distribution cables having multiple buffer tubes with each comprising a plurality of optical fibers require that a particular buffer tube be accessed and the appropriate optical fibers be located, severed and extracted. In one example, the distribution cable may be an ALTOS® dielectric fiber optic cable available from Corning Cable Systems LLC of Hickory, N.C. The ALTOS® dielectric cable is a lightweight cable designed for both buried conduit and aerial deployment. By terminating the one or more optical fibers and transitioning them out of the distribution cable, any bending strain that the cable is subjected to will cause a length differential between the distribution cable and the terminated optical fibers. In a worst-case, the terminated optical fibers may fail under an excessive tension load. In addition to tension on the optical fibers, tension may be placed on the distribution cable and enclosures when the cable assembly is back-pulled through a conduit, sheaves or rollers. Furthermore, cable assemblies that utilize fan-out tubes routed to one side of the distribution cable may snag and eventually break under excessive pulling forces.
Accordingly, there is a specific and unresolved need for a factory-prepared fiber optic distribution cable including at least one mid-span access location for providing access to one or more preterminated optical fibers that has a small enough diameter and is flexible enough to be deployed through a conduit having a relatively small inner diameter or significant bends, or to be deployed using conventional aerial lashing equipment. In addition, there is a specific and unresolved need for a factory-prepared fiber optic distribution cable including one or more optical connection nodes that does not require a highly skilled field technician or extensive field labor to configure the connection nodes after deployment of the distribution cable. There is also a specific and unresolved need for a factory-prepared fiber optic distribution cable including one or more rugged, low profile optical connection nodes capable of withstanding excessive tension forces experienced during deployment of the distribution cable. It is also desirable in an FTTx fiber optic network to provide a fiber optic distribution cable including any desired number of optical connection nodes at a mid-span access location for permitting a less experienced and less skilled field technician to readily connect an optical fiber of the distribution cable to an optical fiber of a branch cable or a drop cable.